Ernest I, Duke of Saxe-Coburg and Gotha (; 2 January 1784 – 29 January 1844), was (as Ernest III) the last sovereign duke of Saxe-Coburg-Saalfeld and from 1826, the first sovereign duke of Saxe-Coburg and Gotha. He is a patrilineal ancestor and great-great-great-grandfather of Queen Elizabeth II.